This invention relates to glazings, and in particular to laminated glazings having high intrusion resistance.
Glazings for automotive use comprise safety glass which may be laminated (widely used for windscreens) or toughened (widely used for sidelights). Each type of glazing provides some degree of impact resistance, but laminated glazings have certain advantages over toughened glass. Although laminated glazings are more expensive to manufacture than toughened glass, it would be desirable for all automotive glazings to be laminated to give improved intrusion resistance and to improve occupant retention in collisions.
Laminated glazings are generally prepared by adhering an impact-resistant layer between two pieces of glass. To be most effective, this impact-resistant layer must be rigid and resistant to penetration from blunt or sharp instruments such as crowbars, hammers, pick axes, and the like. Moreover, the impact-resistant layer, in combination with the glass plies, must be sufficiently thin and light-weight to be suitable for automotive applications. In an example of a conventional impact-resistant laminated glazing, a 3-mm thickness layer of polycarbonate is laminated between two 2-mm thick glass plies through a 0.76-mm thick adhesive interlayer to make a laminate that is more than 8 mm thick. Unfortunately, this laminate, to be effective, is too thick for many automotive glazing specifications, which require a total thickness of less than about 5 mm.
In view of the deficiencies in the art of intrusion-resistant glazings, it would be advantageous to find a more suitable impact resistant layer that meets all of the